Control system for electric heating



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CONTROL SYSTEM FOR ELECTRIC HEATING Filed June 29, 1956 2 Sheets-Sheet 2m5 F'G-G INVENTOR oo WILLIAM C. HACKMAN QM j. #W4

ATTORNEY United States Patent O CONTROL SYSTEM FOR ELECTRIC HEATINGWilliam C. Hackman, Silver Spring, Md., assigner to American EnergeticsCorporation, a corporation of the District of Columbia y Application.lune 29, 1956, Serial No. 594,815

8 Claims. (Cl. 219--20) The present invention relates to electriccontrols and more particularly to automatically controlled switchingarrangements for electric heating systems or the like.

Automatic control systems for electric heating systems :such as electrichot water heaters or the like are Well known. The conventional electrichot water heater has been provided with a plurality of electric heatingunits and various control circuits and devices have been arranged tocontrol the connection of energizing electric current to the heatingunits in accordance with demand. It has been found that the connectionof electricity to all the heating units instantaneously at the moment ofdemand is not entirely satisfactory because the large amount of currentthereby required may be harmful to the switching contacts and the powersource. Furthermore, the `simultaneous energization of all ofthevindividual heating elements at the rst moment of demand when thewater to be heated is relatively cold will release large quantities ofenergy and cause unpleasant pounding due to the gases which are therebyinstantly released. Also, high capacity and relatively expensive relaysand switch contacts must be provided if simultaneous automatic controlof a plurality of heating units is to be provided.

It is therefore a principal object of the present invention to providean improved automatic electric control for electric heating systems ofthe type having a plurality of individual heating elements.

Another object of the invention is to provide an improved automaticallycontrolled electric switching mechanism especially arranged forcontrolling the connection of electricity to individual ones of aplurality of electric heating elements as used in a water heater inaccordance with both demand and the temperature of the water.

According to the invention, the heating system such as an electric waterheater having a plurality of individual electrically energized heatingunits is provided with an automatically controlled electric switchingsystem for connecting electricity to the individual heating units in apredetermined order in accordance with either the demand for heat orpressure rand the momentary temperature of the water within the heater.The arrangement may be such that the heater is controlled to operateover a range of temperatures from a minimum to a maximum such as from160 to 180 Fahrenheit. When the condition of the heating system, suchyas indicated for example by the temperature or pressure of the water,falls below the minimum, a demand for heat is established by a suitabledemand device which closes a circuit to energize preferably only one ortwo heating units. As the cond it10n or temperature of the heatingsystem rises and continuesto rise, the electric controls of theAinvention are effective to progressively energize additional heatingunits until all of the heating units may be energized or until themaximum temperature or condition is reached. When the maximum desiredtemperature or condition of water 1n the heater or of the heating systemis reached, the control system of the invention functions to instantlydisconnect the electricity to all of the individual heating PatentedAug. 19, 1958` units that at that time may be energized and until the`temperature or condition of the heating system thereafter falls to theminimum value, none of the heating units will be energized. It shouldtherefore be apparent that the instantaneous application of largeamounts of electrical and heat energy at a time when the condition ortemperature of water in the heater is relatively low or at the minimumis prevented by the control system of this invention.

Another object of the invention is to provide an irnproved automaticallycontrolled switching system for an electric heating system that isarranged to use relatively inexpensive switching contacts withrelatively small current ilow through the contacts and consequent longconr tact life.

Further objects, features and the attending advantages of the inventionwill be apparent with reference to the following specification anddrawings in which:

Fig. 1 is a side elevational view partly in section of the automaticallycontrolled heater unit controlling switches of the invention;

Fig. 2 is a front view partly in section as seen from right to left ofFig. 1;

Fig. 3 is a cross-sectional view in the direction of the arrows on theline 3 3 of Fig. 1;

Fig. 4 is a fragmentary sectional View on the line 4--4 of Fig. 2;

Fig. 5 is a detailed sectional view on the line 5 5 of Fig. l;

Fig. 6 is a circuit diagram for wiring the switches to a plurality ofelectric heating units and a single phase alternating current or adirect current supply; Fig. 7 is a circuit diagram to show a modifiedform of wiring for the switches when used with a lthree-phasealternating current supply; and

Fig. 8 is a switching circuit diagram for the demand device to controlthe heating unit switches.

IFor a more complete description of the mechanical arrangement of theelectric switching system of the invention, reference is now made toFigures 1 through 5 of the drawings. For purposes of simplification, theheating system such as a water heater is not shown, although it shouldbe understood that the invention may be used for any such applicationwhere a plurality of electric heating units are to be controlled.

The electric control switches 1th through 2l which mayy be of anexpensive low current capacity type aremounted within a suitable housingor enclosure 4generally shown at 22 and for which no details aredescribed since such housing maybe of any suitable form or arrangementrobvious to those skilled in the art. A thermostatic bellows or bulb 23is also mounted within the housing 22 and is connected by the tubing 24to a suitable temperature or pressure sensing bulb (not shown) in theheating system to be controlled. This arrangement is conventional andprovides that the ybellows plunger 25 will move upwardly as seen on thedrawing when the temperature or pressure of the heating system rises.

One end of a lever arm 26 is pivoted at 27 to the housing 22 and theother end is pivotally connected at 28 to a vertically movable switchactuating arm 30. The actuating arm 30 is normally urged downward by thetension of the coil spring 31 so that the lever arm 26 is brought intoengagement with the bellows plunger 25. Therefore, the switch actuatingarm will assume a vertical position varying in accordance with theposition of the thermostatic 'bellows plunger 25 and thus proportionalto the temperature or pressure of the heating system such as indicatedby the condition of the Water within a water heater. Obviously, theswitch actuating arm is guided in its verti-` cal movement by suitable`bearing slideways carried by 3 the housing 22'and not shown in detailin order to simplify the drawings.

The switches 10 through 15 are secured to a U-shaped switch-,supportingframe 35 ,that is rotatably mountedvon a verticalpost 36' supported toone side of theV switching arm 30within the housing. 22:Threaded.collars 37 and 3,8' may adjustably predetermine theverticalpositiono theswitch-,supporting frame, 35; Similarly,vswitches1,6` throughZl are secured to the U-shaped,switchfsupporting framed()that isrotatably journalledionthe vertical post 41 by means ofthethreaded collars 42, 43.

It willbe noted that switch actuating camplates 45 through t)Iaresecuredby means of boltsll through 56, respectively to the switchactuating, arm 3,0. Each Vof thswitcheslf through21A is p rovided. withone of the spring,y loaded, plungers. 60, through 71. to, be` depressedagainstspring ,fr-)roel for closinglthe respective4 switch contracts.Normally the spring loading ofthe switch plungers through 7 Lis sucentto pivotally move the switchsupporting frames-35 and40 yawayfromthe switch actuaiting arminsteadof closing anyof-the respective switchcontacts. However, an electromagnet- 75l is mountedas shown withinthehousing 22fand is provided with a pole piece 76 arcuately shapedas:shown in detail inFig.,y 5 for cooperation withmagnet armature pieces77 and 78 that are carried by the switch framesfand 40 respectively.

Considering also Fig.,8 of the drawings, whenever there is. a, demandfonheat, themagnet or relay 75 is energized by a circuit includingconductors 73, 74 controlled by demand device contacts 480 (assuming the1o;w water contacts 81 and the manual switch contacts 82 are bothclosed), andthearmatures '77 and-78; are attracted to thereby pivotthe;,switchframe s;35 and 40 towards the yswitch actuating arm 30andcause; respective ones-'ofthe switchplungers 60 through 71-toybe.`depressed depending upon the vertical position oftheswitch arm .3.0; `Itwill be noted that each switch actuating cam plate 45-'1through 50. isvertically. adjustable. in its ypositionon the actuating.A arm vlfbymeans of the associatedfastening .bolt and .slot shown in vdetail inFig. 4 of the drawings.A According to the invention, the preferredadjustmentis such that only switches 101and 21 will be closed at a timewhen the temperature within the heatingsystem is at or below the minimumand while the electromagnet 75k is energized by closure of the: demandthermostatic contacts. (not shown). Thereafter, as the temperature ofthe heating system is .raised by heat supplied from heating unitscontrolled by switches and 21, the; bellows 23 will expand to raise theswitch arm 30 and progressively close: switches 11, 20, then switches12, 19, and so forth until either all switches 10 through 21 are closedwith all heating units energized or the temperature of theheating systemrises to the maximum point at which time. the demand device opens itscontacts 80 to deenergize the electromagnet 75. When the electromagnet75 de-energizes, the switch supporting frames 35=and140 pivot away fromthe actuating arm vso that all switches 10.'.through 21aresimultaneously opened and their associated heating units de-energized.'The arrangement may be such that when the heater is first connected andthe water is cold, only switches 10 and 21 will be closed but if theminimum and maximum range of control is of close tolerance, then afterthe temperature of the water falls to the minimum range from the maximumrange, all or most of the individual switches 10 through 21 will beenergized. At ythis time, water lpounding would be avoided since thetemperature ofthe water is already relatively high.

Alternatively, if desired, the switch operating cams-45, 46 or 47 may beadjusted to cause the simultaneous operationand closure of switches10-12 and'19-21 at the moment of demand when the electromagnet 75 is rstenergized. However, it is preferred to position the cams 45 throughSsuch that .onlyswitches 10v and 21 will be closed at the momentofdemandassuming that the-.temperature of the Water Within the heater isquite cold and well below theminimum value as predeterminedbythesettingof'the automatic demand device controlled bellows 23.

The tension of spring 31 may be adjusted by the screws at the top andbottom to in turn adjust the maximum temperature to be reached. iForinstance, the spring would probably be adjusted so that there would be awater temperature range of from 160 minimum to 180 maximum. However, ifVa 200 maximumwas desired,- thetensionon the spring. 31 could beincreased to olsetthepressure bellows 23 and the thermostat or; pressureswitch would-likewise be adjusted for this increased maximumtemperature.

Fig. 6 of the drawingsshows the wiringA connections between-the switchcontacts'10-21 and a plurality of individual heating elements throughY111. Either a single phase alternating current or a direct currentsource is shown to be connected at terminals 112, 113. Terminal 112connects to a distributionbusbar.114,Whichisfin turn, connected toA acontact ofeach of,` switches, 1.0 through 21'; The other contactofeachofswitches, 10 through 211 is respectively connected toone endof one ofthe heating elementswl()4 through 111. The ,other ends of heatingelements, 1,00` through 104 areA connected th1' ough ,fu sen 115to,terminal 11.3. Similarly, theothcr. ends ofheatingelements104..through.107 also4 arel connected through, fuseA11,6, and, elements 108 through. 111;

also` are connected through fuse 117 to terminalv 113. Sincethecurrent-suppliedto each heatingelement'is con-A trolled by a,singleoneoftheswitchesll) throughl 21, such switches may. be. simple andinexpensive with rela,- tively low current` contacts.

Fig. 7 ofv the drawings shows a modied. circuit arrangement forconnection-to a three-phaseA alternating current f supply atterminals.120, 121 and 122. In; this; arrangement the distribution bus bar isseparated; into threeinsulated sections123, 124 land 125,` andthe returncircuits from fuses`115, 116 yand:117 areconnectedgto a respective`three-phaseterminalr 122, .121, andg f instead ofto asingleterminalsuch as was shownat 113;,in-Fig; 6 of Arthejdrawings.

It should-be understood` that various modications may beTmade-withinthespiritof theinventionandxthe scope of=theyappcnded claims. Forexample, the inventionis not limited to a specic number off'individualcontrol switchesy andheating units controlledthereby. Although there hasbeen,spec ica1ly described a ,form of the Vinverttion nwhich;twoheatingunits areI initially. energized upon demand'whentheheatinggsystem conditionis at;a minimum, obviously oneor more,heating. units.l may, be arranged'to'be energizedtat that .time so long`as ythenumber energized atthat timeis less than the-number to'beultimately energized as the conditiontrisestowardsthe maximum..`

Throughout the specification,- reference hasfbeen made to .a demanddevice for controlling the pressure inthe bellows- 235 It. should: beunderstood that suchdemand devicefmay be controlled'by either thetemperature'of pressure of'theewater in the heatingsystem, as desired;In the .claimsiitwill be understoodthat the condition of the heating`system may be indicatedand sensedby either thetemperature or pressureofthe heatingfsystem water for controlling thevdemand device.

What is claimed is: i

1. In a controlfor an electric heating system ofthe type havingavplurality of-e1ectrically` energized heating units, a plurality ofcontrol-switches-adapted tube-.operated lfor connectingV electric energyto respective ones oftheheatingunits, switch control means movable in adirectionrelative to saidl control switches in response'to a riseinftemperature of the heating systemrand normally out ofengagementlwithsaidI control'switches, and demand means-operative torespond'toa temperautre vof the heating-system at or below.apredetermined minimum value. for movingl saidvplurality ofswitches-into^th`e path or movement ofsaidcontrol means-to f engage and-opcrate respective ones of said control switches depending upon theposition of said control means as determined 'by the temperature of theheating system.

2. The invention of claim 1 wherein said control means is adapted toengage and operate progressively more of said control switches as it ismoved in response to a rise in temperature of the heating system whilesaid demand means is operative.

3. In a control for an electric heating system of the type having aplurality of electrically energized heating units, a plurality ofcontrol switches adapted to be operated for connecting electric energyto respective ones voli the heating units, switch control means movablein a direction relative to said control switches in response to a risein temperature of the heating system and normally out of engagement withsaid control switches, demand means operative to respond to atemperature of the heating system at or below a predetermined minimumvalue for moving said plurality of switches into the path of movement ofsaid control means to engage and operate respective ones of said controlswitches depending upon the position of said control means as determinedby the temperature of the heating system, said demand means being alsooperative to respond to a maximum temperature of the heating system formoving said switches out of the path of movement of said control meansto thereby restore all of said switches to their unoperated conditionsupon maximum temperature being reached.

4. The invention of claim 3 wherein said control means is adapted toengage and operate progressively more of said control switches as it ismoved in response to a rise in temperature of the heating system Whilesaid demand means is operative.

5. The invention of claim 1 wherein said control means is adapted toengage and operate a minimum number of said switches less than the totalnumber of said switches when said demand means is operative and thetemperature of said heating system is at or below a predeterminedminimum value,

6. The invention of claim l wherein said control means is adapted toengage and operate a minimum number of said switches less than the totalnumber of said switches when said demand means is operative and thetemperature of said heating system is at or below a predeterminedminimum value and is adapted to engage and progressively operateadditional ones of said control switches as it is moved in response to arise in temperature of the heating system above the predeterminedminimum value.

7. The invention of claim 3 wherein said control means is adapted toengage and operate a minimum number of said switches less than the totalnumber of said switches when said demand means is operative and thetemperature of said heating system is at or below a predeterminedminimum value.

8. The invention of claim 3 wherein said control means is adapted toengage and operate a minimum number of said switches less than the totalnumber of said switches when said demand means is operative and thetemperature of said heating system is at or below a predeterminedminimum value and is adapted to engage and progressively operateadditional ones of said control switches as it is moved in response to arise in temperature of the heating system above the predeterminedminimum value.

References Cited in the le of this patent UNITED STATES PATENTS1,194,165 Fry Aug. 8, 1916 1,883,766 Cox et al. Oct. 18, 1932 2,161,614Cunningham June 6, 1939 2,419,083 Myers Apr. 15, 1947 2,598,036 Cahillet al May 27, 1952 2,706,240 Hackman Apr. 12, 1955 2,788,416 KilburyApr. 9, 19,57

UNITED STATES PATENT GFFCE CERTIFICATE cF @carence Patent Non 2,848,588August l@y 1958 William C liackman lt is hereby certified that errorappears in the above numbered patent requiring correction and that the`said Letters Patent should read as cors rected below.

In the grant, lines 2 and 3, for "assignor to Energetics Corporation, acorporation of the' District of Columbia," read ma assignor of onemllalfto American Energetics Corporation,n a corporation of the District ofColumbia9 umg line l2, for "Energetics Corporationj its successors" readm William C Hackman, bis heirs or assigns, and American EnergeticsCorporationy its successors w; in the heading to the printedspecification3 lines 3, 4. and 5y for "assignor to American EnergeticsCorporation, a corpom ration of the District of Columbia" read massignor of one=hal` to American Energetics Corporation, a corporationoi tbe District of Columbia ===f This certificate supersedesCertificatev of Correction issued Cctober 21st, 1958,

Signed and sealed this Elst day of Maren D959,

(SEAL) Attest:

KARL n, AXLINE i ROBERT c. WATSON Attesting officer commissioner ofPatents UNITED STATES PATENT OFFICE CERTIFICATE OF CORRECTION Patent No,2,848,588 August 19, 1958 William C Hackman lt is hereby certified thaterror appears in the above numbered patent requiring correction and thatthe said Letters Patent should read as cors rected below, l

In the grant, lines 2 and 3, for "assignor to Energetics Corporation, acorporation of the District oi` Columbia,'Y read a assignor of one-halfto American Energetics Corporation, a corporation of the District oiColumbia, en; line l2, for HEnergetics Corporation, its successors" readWilliam C Hackman, his heirs or assigns, and American EnergeticsCorporation, its successors u; in the heading to the printedspecification, lines 3, 4 and 5, for Hassignor to American EnergeticsCorporation, a corpo ration of the District of ColumbiaH read m assignorof oneehalf to American Energetics Corporation, a corporation of theDistrict of Columbia This certificate supersedes Certificate' ofCorrection issued October 21st, 1958,

Signed and sealed this Elst day of March 1959,

(SEAL) Attest:

KARL AXLINE ROBERT c. wATsoN Attesting Officer Commissioner of Patents

